1. Field of the Invention
One embodiment relates to a sealing element comprising a closure lid for sealing off the outer part of a homokinetic joint, relative to a pipe or a shaft. The sealing element is connected to the outer part, as well as to a sealing assembly having such a sealing element.
The homokinetic joints are configured with an inner hub and an outer hub and which have multiple raceways, and which are assigned to one another in pairs. These raceways receive raceway balls guided in a cage and are accommodated to transfer torque between the inner hub and the outer hub, and sealing toward the outside. These homokinetic joints can be used in longitudinal or side shafts of motor vehicles. These are provided with a lubricant that ensures good behavior of the homokinetic joints with regard to friction or wear.
To prevent lubricant from exiting from the joint, and to prevent penetration of dirt particles or similar foreign bodies, these joints are sealed.
This sealing is done by way of elastomer parts, caps and closure lids wherein the outer joint parts are sealed, relative to the shaft journal, using folded or rolled bellows, and sealed with sheet-metal lids at their outer flange surfaces.
The elastic sealing elements are positioned between the metallic surfaces to achieve sealing. These metallic surfaces lay one on top of the other, since the metallic surfaces cannot reliably prevent exiting of the lubricant during operation. This is because the surfaces are not machined precisely, but the sealing elements used are subject to wear.
2. The Prior Art
One sealing assembly having a homokinetic rotary joint is known from German Patent DE 198 57 460 C2 also published as U.S. Pat. No. 6,354,604, which comprises an outer joint part having at least one opening on an axial end, an inner joint part inserted into this, having a drive shaft connected with it, and roller bodies that act between the outer joint part and the inner joint part, serving to transfer torque, whereby at least one sheet-metal element having a ring surface rests on a face surface of the outer joint part, and the outer joint part and the sheet-metal element are braced relative to one another, and a first surface—right ring surface or face surface—has a surface structure with elevations and depressions, and the other surface, in each instance—ring surface or face surface—forms a planar counter-surface. In this connection, the plastic-elastic sealing means is introduced between the ring surface and the face surface, and is formed into the interstices of the surface structure in the elevations of the planar counter-surfaces.
A sealing assembly for a homokinetic rotary joint having an inner joint part that is connected with a shaft journal, and having an outer joint part that is sealed, relative to the shaft journal, with a folded bellows, and having a closure lid on the outer joint part, which is braced between the outer joint part and the inner joint part with an edge region, is described in DE 197 36 546 C 2, also published as U.S. Pat. No. 6,237,920 in which the closure lid is connected with the outer joint part by means of an adhesive layer consisting of a sealant, which layer is supposed to act to provide a seal relative to the flange surface and relative to the closure lid.
Sealing of homokinetic joints is one of the prerequisites for operational reliability and for proper functioning of the homokinetic joint, in each instance. Taking these requirements into account, there are different solution proposals. For example, DE 24 19 236 A describes a homokinetic joint that is sealed off, on one side, by means of a cover part, whereby this cover part is connected between a shaft and the outer ring of the homokinetic joint. On the opposite side, sealing of the homokinetic joint takes place by means of a rubber bellows.
A joint assembly having sealing means has become known from DE 10 2006 006 441 A 1, which was also published as U.S. Patent Application Publication No. 2007191121 which is formed from a lid and a membrane part. The lid is disposed on one side, and the membrane part is disposed on the opposite side; they are connected with the outer part of the homokinetic joint and the subsequent components, in each instance.
A homokinetic rotary joint for a longitudinal drive shaft having optimized crash behavior is described in DE 196 52 100 C 1 and which is also published as U.S. Pat. No. 6,171,196. This homokinetic rotary joint is also sealed off, on the right and left side, with regard to external influences, on the one side by way of a known rolled bellows, and on the other side by way of a lid that is provided in a tubular shaft. This lid is primarily disposed in order to guarantee telescoping or unhindered telescoping of the individual parts in the case of a crash, and it also takes on certain sealing functions in this connection.
A homokinetic joint of this type is described by DE 43 44 177 C 1, which is also published as U.S. Pat. No. 5,582,546, whose geometric dimensions of the individual functional parts are coordinated with one another in such a manner that the inside diameter of the outer joint part or of the subsequent tubular shaft that follows the clear space taken up by the inner joint part during operation, when displacement movements occur, is smaller, in the direction towards the tubular shaft, than the outside diameter of the inner joint part. Thus, undisturbed telescoping of the individual components of the homokinetic joint in the case of a crash is supposed to be made possible. Sealing of the homokinetic joint in the direction of the tubular shaft takes place by way of a lid disposed in the tubular shaft, and on the opposite side by way of a rolled bellows that is provided.
One solution that relates to a sealing element and a sealing assembly on a homokinetic rotary joint has become known from DE 101 20 884 A 1, which is also published as FR 2 824 122. The sealing element consists of a ring disk having face surfaces on both sides. In the ring disk is provided at least one circumferential groove, and in the groove of the sealing element is inserted and permanently attached a sealing ring made of permanently elastic sealing mass. The sealing element is arranged between the cover and the outer port of the homokinetic rotary joint.
It is a disadvantage of these solutions that additional sealing elements/sealing materials are used to attach the sheet-metal lid and to seal the homokinetic joint, in order to achieve a good seal of the homokinetic joint. The disadvantage is particularly due to the fact that elastic sealing elements and adhesives that are used harden and become porous after a certain period of time, so that it cannot be prevented that lubricant exits to the outside from the interior of the homokinetic joint, and in return, undesirable foreign particles can get into the interior of the homokinetic joint.
It is furthermore disadvantageous that when welding a pipe or a shaft to the outer part of the homokinetic joint, elevated temperatures occur, which also have a negative effect on the sealing properties of the adhesive or sealing elements that are used.